We present a straightforward and accurate method for measuring the birefringence of chiral waveguides. Due to the chiral nature of these devices, the supported modes are elliptical, enabling direct access to their linear birefringence characteristics. Consequently, determining the linear birefringence reduces to measuring the device's Mueller matrix. This method is particularly effective when the linear birefringence is comparable in magnitude to the circular birefringence (on the order of 10-5). The technique is applied to study the impact of humidity on sol-gel-based chirowaveguides. Four distinct linear birefringence contributions are identified and measured: (1) Opto-geometrical birefringence, resulting from the waveguide geometry and modal TE/TM decomposition; (2) tensile stress-induced birefringence (similar to 10-4), linked to the waveguide fabrication process; (3) compressive stress-induced birefringence, which increases with humidity due to material swelling; and (4) residual diagonal birefringence (similar to 10-6), attributed to slight asymmetries in the rib waveguide cross-section.

We describe a very simple and efficient gram-scale synthetic pathway toward Boranils substituted directly on the boron center by 1,1'-bi-2-naphthol derivatives (BINOL). Properties of the resulting BINOL-Boranils were investigated by nuclear magnetic resonance (NMR), UV-visible, fluorescence, electronic circular dichroism (ECD), and circularly polarized luminescence (CPL) spectroscopies. Insight into the molecular structure is also provided based on single-crystal X-ray diffraction experiments. These chiral dyes typically feature high molar absorption coefficients in the range of 35,000 to 90,000 M-1·cm-1, absorption dissymmetry factors (g abs) in the range of 2.5-5.5 × 10-4 at the maximum wavelength of absorption of Boranils, and CPL brightness up to B CPL = 5.4 M-1·cm-1.

We present a straightforward and accurate method for measuring the birefringence of chiral waveguides. Due to the chiral nature of these devices, the supported modes are elliptical, enabling direct access to their linear birefringence characteristics. Consequently, determining the linear birefringence reduces to measuring the device’s Mueller matrix. This method is particularly effective when the linear birefringence is comparable in magnitude to the circular birefringence (on the order of 10−5). The technique is applied to study the impact of humidity on sol–gel-based chirowaveguides. Four distinct linear birefringence contributions are identified and measured: (1) Opto-geometrical birefringence, resulting from the waveguide geometry and modal TE/TM decomposition; (2) tensile stress-induced birefringence (∼10−4), linked to the waveguide fabrication process; (3) compressive stress-induced birefringence, which increases with humidity due to material swelling; and (4) residual diagonal birefringence (∼10−6), attributed to slight asymmetries in the rib waveguide cross-section.

Chiral lanthanide complexes hold great potential in developing advanced circularly polarized luminescence (CPL) materials in the near-infrared (NIR) wavelength range. While various ligands, such as β-diketonates and biphenols, have been successfully used to sensitize NIR emission of lanthanide ions, little attention has been paid to regulating CPL behaviors via ligand modification. In this study, we report the synthesis, structure, luminescence, and chiroptical properties of a pair of novel air-stable Shibasaki-type Yb(III) enantiomers supported by 3,3'-fluorinated binaphthol (F2BINOL). Compared to their nonfluorinated counterparts, these fluorinated complexes exhibit larger dihedral angles between the two naphthyl moieties and more distorted octahedral coordination environments around the Yb(III) ion, leading to increased overall crystal field splitting. These structural modifications result in enhanced photophysical properties: the luminescence lifetime (τobs), sensitization efficiency (ηsens), and quantum yield (QY) improve from 2.1 µs, 38%, and 0.7% to 2.7 µs, 63%, and 1.8%, respectively. Additionally, the dissymmetry factor (glum) and CPL brightness (BCPL) at 963 nm increase by 32% and one order of magnitude, respectively. The scope of such chemical modification is broad, potentially encompassing a variety of BINOL derivatives, offering a unique platform to further elucidate the relationship between structural and electronic properties and CPL activity in lanthanide systems.

The realization of integrated active optical systems is crucial for the use of components such as amplifiers, lasers or photodetectors on a chip. Alumina (Al2O3) doped with erbium is a promising material for the realization of various active functions. Indeed, the low propagation losses of Al2O3, the rare earth compatibility and its wide transmission band makes Al2O3 suitable for a wide range of applications. Nevertheless, current methods for producing such waveguides are often costly and difficult, requiring complex and potentially loss-making processing steps like etching. In this context, Pulsed Laser Deposited (PLD) combined with lift-off is a relevant method for avoiding etchings. The process is composed of three main steps: photolithography, PLD and lift-off. In this work, we present how the different steps have to be optimized to make suitable waveguides for light propagation. Notably, photolithography needs a precise cross-section profile to obtain smooth sidewall, to ease lift-off and get high resolution patterning. For PLD, SEM images showed the importance of plume directivity and orientation in the PLD chamber to achieve a good control of the waveguide shapes. Finally, we also have shown that the Erbium photoluminescence is dependent on the annealing temperature. These results highlight the essential parameters which need to be precisely controlled to achieve accurate microstructures by liftoff processing performed in PLD layers, paving the way for the demonstration of low-loss waveguides and fully integrated erbium laser without etching.

Chiral, enantiopure Yb(III) complexes are able to emit circularly polarized luminescence (CPL) in the near infrared (NIR) wavelength region, quantified by the dissymmetry factor (glum). Due to crystal field splitting (CFS), the excited state 2F5/2 consists of three mj' sublevels, which are populated in accordance with the Boltzmann distribution. Consequently, room temperature CPL spectra are the sum of various - either positive or negative – contributions, that are practically impossible to quantify. Thanks to the use of an advanced setup enabling CPL measurements over a range of temperatures (300 to 4 K), the interrelation of CFS, glum and temperature was demonstrated on the example of a pair of enantiopure Yb(III) com-plexes. It was thereby confirmed that each mJ’ sublevel gives an independent contribution to the overall CPL spectrum. Hence, the CPL spectra of chiral lanthanide complexes were found to be indeed strongly temperature-dependent, as is the glum dissymmetry factor, as a consequence of the variation in thermal sublevel population. These results were additional-ly interpreted in the framework of multireference wave-function calculations.

This article reports a detailed mechanistic and kinetic study of an unusual photoreaction leading to the (diazonia)tetrabenzonaphthacene skeleton. The photo-triggered double intramolecular nucleophilic aromatic substitution (SNAr*) has been investigated by varying the leaving groups. Photoreaction quantum yields have been determined and mechanistic insights have been supported by theoretical calculations using DFT and TD-DFT methods. Additionally, we show that this light-triggered formed diazonia constitutes a potent photosentitizer with a singlet oxygen generation quantum yield of 0.55, both in organic solvents and in water, which is an extremely relevant value in view of PDT applications or use as an oxidation photocatalyst in aqueous media. Once again, the experimental observations were supported by TD-DFT calculations showing a large density of triplet states below the S1 excited state along with large spin-orbit couplings. The reaction is not restricted to solutions but can also occur in solid PDMS matrices thus allowing for photochemical encoding of information that will progressively vanish upon prolonged UV-exposure.

This article outlines the synthesis and comprehensive characterization of a pair of Er(III) enantiomers with controlled helicity. These complexes exhibit a near-infrared circularly polarized luminescence (NIR-CPL) signature with high glum values of ± 0.66 at 1519 nm at room temperature. However, due to a large number of potential transitions at this temperature owed to the crystal field splitting, the CPL pattern likely results from overlapping of many positive and negative contributions. This study explores how reducing the effective bandwidth affects the CPL spectral analysis. Practical insights are provided for measuring CPL spectra, highlighting the importance of resolving peak positions with opposite signs to accurately determine glum values.

Abstract We present a comprehensive study on the effect of humidity on organically modified sol-gel glasses (ormosils) thin films and related-microstructures, using optical characterization methods.Using a Mach-Zehnder interferometer and a polarimetric setup, we quantitatively measure the variations in refractive index and linear birefringence induced by changes in ambient relative humidity. Our findings unveil the high sensitivity of the material's refractive index to humidity, predominantly attributed to the hygroscopic nature of the polyethylene glycol (PEG) component embedded within the ormosils.Furthermore, We show that stress-induced birefringence during the deposition of the sol-gel layers is partially released in the structured layers compared to the planar one. The remaining stress is reduced by the effect of humidity in a linear relationship in which the proportionality factor is higher in the planar layers. The results shown here shed new light on the complex relationship between humidity and sol-gel derived materials and contribute to the understanding of the mechanisms behind their sensitivity to humidity.

A chiral Yb( iii ) complex bearing a conjugated chromophoric ligand exhibits potential as NIR-to-NIR chiroptical probe for biological purposes.

Circularly polarized luminescence (CPL) is a fast growing research field as a complementary chiroptical spectroscopy alternative to the conventional circular dichroism or in the quest of devices producing circularly polarized light for different applications. Because chiroptical signals are generally lower than 0.1%, conventional chiral spectroscopies rely on polarization time modulation requiring step-by-step wavelength scanning and a long acquisition time. High throughput controls motivated the development of CPL spectrophotometers using cameras as detectors and space polarization splitting. However, CPL measurements imposes careful precautions to minimize the numerous artifacts arising from experimental imperfections. Some previous work used complex calibration procedure to this end. Here we present a rigorous Mueller analysis of an instrument based on polarizations space splitting. We show that by using one camera and combining spatial and temporal separation through two switchable circular polarization encoding arms we can record accurate CPL spectra without the need of any calibration. The measurements robustness and their fast acquisition times are exemplified on different chiral emitters.

Redox-active conductive supramolecular gels involving highly ordered chiral assemblies of small organic molecules are very promising soft materials for many applications ranging from catalysis to electronics. However, combining all these properties in the same material has so far remained a difficult task. We now report the synthesis and detailed structural, rheological and electrical characterizations of supramolecular gels obtained by self-assembly of a dicationic low molecular weight gelator incorporating a redox-active 4,4’-bipyridinium unit. These molecules have been shown to self-assemble in pentanol to form chiral hollow core-shell cylinders eventually yielding dendritic clusters inducing gelation. We also showed that the optical, rheological and electrical properties of the gels can be tuned by addition of ionic additives. Careful control of the formation of charge-transfer complexes between viologens and iodides have led to a robust, transparent, conductive and chiral gel. The gelation process and the structure/properties of the gel have been thoroughly investigated by UV-Vis and ECD spectroscopy, rheology, bright-field microscopy, SAXS, AFM, electrochemical and impedance measurements.

Lanthanide ions have attracted great interest owing to their optical and magnetic properties. Single-molecule magnet (SMM) behavior has been a fascinating science for thirty years. Moreover, chiral lanthanide complexes allow the observation of remarkable circularly polarized luminescence (CPL). However, the combination of both SMM and CPL behaviors in a single molecular system is very rare and deserves attention in the design of multifunctional materials. Four chiral one-dimensional coordination compounds involving 1,1 '-Bi-2-naphtol (BINOL)-derived bisphosphate ligands and the Yb(iii) centre were synthesized and characterized by powder and single-crystal X-ray diffraction. All the Yb(iii)-based polymers displayed field-induced SMM behavior with magnetic relaxation occurring by applying Raman processes and near infrared CPL in the solid state.

A series of molecules that possess two quinolines, benzoquinolines, or phenanthrolines connected in a chiral fashion by a biaryl junction along with their water-soluble derivatives was developed and characterized. The influence of the structure on the basicity of the nitrogen atoms in two heterocycles was examined and the photophysical and chiroptical switching activity of the compounds upon protonation was studied both experimentally and computationally. The results demonstrated that changes in the electronic structure of the protonated vs. neutral species, promoting a bathochromic shift of dominant electronic transitions and alternation of their character from π-to-π* to charge-transfer-type, when additionally accompanied by the high structural flexibility of a system, leading to changes in conformational preferences upon proton binding, produce particularly pronounced modifications of the spectral properties in acidic medium. The latter combined with reversibility of the read-out make some of the molecules in this series very promising multifunctional pH probes.

Circularly polarized luminescence activity from new cationic water soluble Sm( iii ) and Eu( iii ) complexes is triggered by one- and two-photon absorption processes. The Eu( iii ) complex is shown to be an efficient NIR-to-RED probe in cellulo .

The combination of physical properties sensitive to molecular chirality in a single system allows the observation of fascinating phenomena such as magneto-chiral dichroism (MChD) and circularly polarized luminescence (CPL) having potential applications for optical data readout and display technology. Homochiral monodimensional coordination polymers of Yb-III were designed from a 2,15-bis-ethynyl-hexahelicenic scaffold decorated with two terminal 4-pyridyl units. Thanks to the coordination of the chiral organic chromophore to Yb(hfac)(3) units (hfac(-)=1,1,1,5,5,5-hexafluoroacetylaconate), efficient NIR-CPL activity is observed. Moreover, the specific crystal field around the Yb-III induces a strong magnetic anisotropy which leads to a single-molecule magnet (SMM) behaviour and a remarkable room temperature MChD. The MChD-structural correlation is supported by computational investigations.

Abstract Lithium niobate is a material of special interest for its challenging functional properties, which can suit various applications. However, high quality 200‐mm LixNb1‐xO3 thin film grown on sapphire substrate have never been reported so far which limits these potential applications. This paper reports the efficient optimization of high quality LiNbO3 thin film deposition on sapphire (001) substrate through chemical beam vapor deposition in a combinatorial configuration. With this technique, flow ratio of Li/Nb can be tuned from ≈0.25 to ≈2.45 on a single wafer. Various complementary characterizations (by means of diffraction, microscopy and spectroscopy techniques) have been performed at different areas of the film (different cationic ratios) in order to investigate the impact of the cationic stoichiometry deviation on the film properties. Close to cationic stoichiometry (LiNbO3), the epitaxial films are of high quality (single phase in spite of two in‐plane domains, low mosaicity of 0.04°, low surface roughness, refractive index and band gap close to bulk values). Deviating from the stoichiometry conditions, secondary phases are detected (LiNb3O8 for Nb‐rich flow ratios, and Li3NbO4 with partial amorphization for Li‐rich flow ratios). LiNbO3 films are of high interest for various key applications in data communications among others.

Chiral halide perovskite nanocrystals have many applications in next-generation optoelectronic devices due to their interaction with circularly polarized light. Through the careful selection of chiral organic surface ligands, control over the circular dichroism (CD) and circularly polarized luminescence (CPL) of these materials can be achieved. However, while recent developments of CD-active perovskites have seen significant advances, effective CPL remains a challenge. Here, we synthesize colloidal perovskite nanoplatelets exhibiting room temperature CPL with dissymmetry factors up to glum=4.3×10^(-3) and gabs=8.4×10^(-3). Methylammonium lead bromide nanoplatelets are synthesized with a mixture of chiral dimethyl benzyl ammonium ligands and achiral octylammonium ligands, the precise ratio of which is shown to be critical to achieving high g-factors. We investigate the competitive binding of these surface ligands using 1H NMR, and use an equilibrium model to demonstrate the ligand affinity. The magnitude of CPL and CD is quantitatively shown to exhibit a linear correlation, such that glum=0.4×gabs. Lastly, by screening several amines with close structures, we show that subtle differences in ligand structure have significant impact on the resulting CD signal of the nanoplatelets. Our findings provide new insights for the effective design of perovskites exhibiting CPL and can facilitate the development of high-performance devices based on circularly polarized luminescence.

Chiral halide perovskite nanocrystals have many applications in next-generation optoelectronic devices due to their interaction with circularly polarized light. Through the careful selection of chiral organic surface ligands, control over the circular dichroism (CD) and circularly polarized luminescence (CPL) of these materials can be achieved. However, while recent developments of CD-active perovskites have seen significant advances, effective CPL remains a challenge. Here, we synthesize colloidal perovskite nanoplatelets exhibiting room temperature CPL with dissymmetry factors up to glum=4.3×10^(-3) and gabs=8.4×10^(-3). Methylammonium lead bromide nanoplatelets are synthesized with a mixture of chiral dimethyl benzyl ammonium ligands and achiral octylammonium ligands, the precise ratio of which is shown to be critical to achieving high g-factors. We investigate the competitive binding of these surface ligands using 1H NMR, and use an equilibrium model to demonstrate the ligand affinity. The magnitude of CPL and CD is quantitatively shown to exhibit a linear correlation, such that glum=0.4×gabs. Lastly, by screening several amines with close structures, we show that subtle differences in ligand structure have significant impact on the resulting CD signal of the nanoplatelets. Our findings provide new insights for the effective design of perovskites exhibiting CPL and can facilitate the development of high-performance devices based on circularly polarized luminescence.

Polarization in photonic‐integrated circuits (PICs) is governed by transverse electric (TE) and magnetic (TM) polarizations due to the planar structure of the chips. Therefore, all states of polarization (SOPs) other than TE and TM, in particular circular polarization, cannot be routed without modification across the chips. Herein, the realization of rib‐channel chirowaveguides supporting elliptically polarized guided modes by combining linear and circular birefringences as predicted by the coupled mode approach is shown. The sol–gel process and the imprint technique to make channel chirowaveguides with different sizes and consequently modulate ellipticity of the eigenmodes from linear to quasicircular are used. Circularly polarized light propagates therefore with a low polarization beating and in particular without handedness inversion. These results open the field of application of PICs to all domains where circularly polarized light is relevant.